Method of cleaning residual pesticide from an agricultural vessel

ABSTRACT

The present invention generally relates to methods of cleaning residual pesticide from an agricultural vessel, and to kits and compositions useful for the practice of such methods.

FIELD OF THE INVENTION

The present invention generally relates to methods of cleaning residualpesticide from an agricultural vessel, and to kits and compositionsuseful for the practice of such methods.

BACKGROUND OF THE INVENTION

Auxin herbicides, such as 2,4-D and dicamba, are highly effective forthe control of broadleaf weeds, particularly weeds that have becomeresistant to glyphosate. Dicamba, for example, causes significant damageto plants even at extremely low application levels.

When a pesticidal composition is sprayed, a residual amount of theactive pesticidal agent typically remains in the tank. This pesticidalresidue, if left untreated, can pose a significant problem for farmersby unintentionally damaging crops and desirable plants. As a result,special precautions must be taken to prepare spray tanks for subsequentuse following the application of pesticides. This problem isparticularly acute for auxin herbicides, such as dicamba, where evensmall amounts of herbicidal residue could result in significant damageto sensitive crop plants.

Due to the high potency of dicamba, three full rinses of the spray tankare traditionally required to ensure zero crop damage from the residue.Typical cleaning methods require the cleaning rinse to stand in thespray tank for at least four hours, and preferably should be allowed tosoak overnight. This process, although effective, is both expensive andcumbersome. The rinses require additional water in the field, and thelong soaking period reduces the time that the equipment is available forspraying crops.

An alternative method of degrading pesticidal residue in the field,which reduces the water use and time required for the farmer to switchto another pesticide, is therefore highly desirable.

SUMMARY OF THE INVENTION

Briefly, therefore, the present invention is directed to methods ofpreparing a tank for use in connection with a second pesticide followinguse of the tank in connection with a first pesticide. In variousembodiments, the first pesticide is an herbicide. The first and secondpesticides may be the same pesticide (e.g., dicamba). In variousembodiments, the method comprises introducing a cleaning mixture into atank containing a residual amount of a first pesticide; the cleaningmixture comprises (a) a source of transition metal ions, and (b) asource of hydrogen peroxide. Optionally, the cleaning solution mayfurther comprise water. The method further comprises allowing thecleaning mixture to remain in the tank for a time sufficient to degradeat least a portion of the residual amount of the first pesticide,thereby forming a waste mixture comprising degradation products of thefirst pesticide; and removing the waste mixture from the tank.

The present invention is further directed to kits for use in cleaning atank following the use of the tank in connection with a pesticide.Generally, the kits comprise a source of hydrogen peroxide and a sourceof transition metal ions.

In preferred embodiments of the present invention, the transition metalions are polyvalent iron ions.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is directed to the expected concentration of dicamba with respectto time on a logarithmic scale as described in Example 5.

FIG. 2 is directed to the reaction rate constant as a function ofinitial hydrogen peroxide concentration as described in Example 5.

FIG. 3 is directed to the reaction rate constant as a function of themolar ratio of iron ions to glyphosate in the reaction mixture asdescribed in Example 5.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, it has been discovered thatthe Fenton reaction may be utilized to provide an economical andeffective means of degrading residual pesticides (e.g., herbicides) inagricultural vessels (e.g., spray tanks)

In the Fenton reaction, in which a source of iron ions is utilized,ferrous iron ions are oxidized by hydrogen peroxide to produce hydroxylradicals:

Fe²⁺+H₂O₂→Fe³⁺+OH⁻+OH.   (1)

A second reaction, in which the iron (III) product compound is reducedin the presence of hydrogen peroxide, makes the Fenton reactioncatalytic with respect to iron:

Fe³⁺+H₂O₂→Fe²⁺+H⁺+HOO.   (2)

In most environments, reaction (2) is several orders of magnitude slowerthan reaction (1), and thus becomes the rate-limiting step where anexcess of H₂O₂ is present.

More generally, other transition metals have also been observed tocatalyze reactions similar to the Fenton reaction, wherein transitionmetal ions react with hydrogen peroxide to produce hydroxyl radicals.For example, the transition metal may be selected from the groupconsisting of copper, vanadium, chromium, molybdenum, tungsten,manganese, cobalt, nickel, cerium, ruthenium, aluminum, antimony, zinc,titanium, tin, barium, and combinations thereof. Preferably, thetransition metal ions are polyvalent. Cobalt is an example of atransition metal known to engage in a Fenton-like reaction with hydrogenperoxide. Accordingly, although the methods, compositions, and kitsdescribed herein are described primarily with respect to the traditionalFenton reaction, which involves polyvalent iron ions as the metalcatalyst, one skilled in the art would understand that the presentinvention encompasses the use of other transition metals as describedabove.

When hydroxyl radicals are produced in the presence of a pesticide, thepesticide is degraded into reaction products that do not retainpesticidal activity. Surprisingly, it has been discovered that thisreaction may be incorporated into an improved process for cleaningpesticidal residue from spray tanks that provides a high level ofeffectiveness and requires significantly less cleaning time thantraditional rinses. The result is a convenient and inexpensive solutionthat is beneficial for both farmers and custom applicators. Inparticular, the methods of the present invention are suitable forin-field applications and also are more rapid than conventional tankcleaning methods. For example, as detailed elsewhere herein, the methodsof the present invention are suitable for tank cleaning that occurs overa period of no more than 30 minutes and, in various preferredembodiments, methods that occur over a shorter period of time (e.g.,less than about 10 minutes, or even less than about 5 minutes).

Generally, the method involves the preparation of an aqueous cleaningmixture comprising a source of transition metal ions (e.g., polyvalentiron ions) and a source of hydrogen peroxide. The cleaning mixture isintroduced into a tank containing a residual amount of the pesticide,and is allowed to remain in the tank for a time sufficient tosubstantially degrade the pesticidal residue. As used herein,“degradation” refers to the process whereby the pesticide decomposesinto reaction products that do not retain pesticidal activity.

Optionally, the present method may incorporate a pre-rinse step, whereinan amount of an aqueous medium (e.g., water) is introduced into the tankprior to the cleaning step. The pre-rinse step is useful to reduce anyexcessive pesticidal residue that may be present in the tank, therebydecreasing the total amount of pesticide that remains to be degraded bythe cleaning solution. The waste product formed by the pre-rinse step,referred to herein as a diluted pesticidal residue mixture, comprises aportion of the residual first pesticide. Typically, at least a portionof the diluted pesticidal residue mixture is removed from the tank(e.g., by spraying) prior to introduction of the cleaning mixture intothe tank.

Typically, the aqueous medium (e.g., rinse water) is introduced into thetank in a volumetric ratio, with respect to the pesticidal residue at atypical pesticidal concentration, of at least about 1:1, at least about2:1, at least about 5:1, at least about 10:1, at least about 20:1, or atleast about 50:1.

Generally, the amount of pesticide remaining in the tank and anyappurtenant apparatus (e.g., spray lines, pumps, etc.) can be reliablyestimated by one skilled in the art based on the size and shape of thetank, the spray apparatus, and the concentration of the first pesticidemixture. In most cases, the amount of dead volume present in a spraytank, and in any equipment connected thereto (e.g., a boom sprayapparatus), will be known to the skilled worker and/or the equipmentmanufacturer, and may be used to obtain a reasonably accurate estimateof the amount of pesticidal residue remaining therein. Once the amountof pesticidal residue remaining in the tank is estimated, appropriateamounts of the sources of transition metal ions and hydrogen peroxideforming the cleaning mixture can be selected for introduction into thetank. More particularly, appropriate molar ratios of hydrogen peroxideto pesticidal residue and to the transition metal ions are disclosedbelow and can be used to determine appropriate quantities of the sourcesof hydrogen peroxide and transition metal ions to form the cleaningmixture.

Where the spray tank is a component of a larger system, for example aboom spray system, the cleaning mixture can also be used to clean thehoses, pumps, and spray nozzles incorporated therein. Typically, watermay be added to the cleaning mixture in an amount sufficient to allowthe cleaning mixture to recirculate through the system (e.g., the boomspray system). The volume of liquid necessary for effectiverecirculation is dependent on the particular equipment to be cleaned,and can be reliably determined by one skilled in the art.

Generally, the amount of water incorporated into the cleaning mixturewill correspond to the amount necessary to effectively recirculate themixture through the system, as described above. This water may beprovided by the source of transition metal ions, source of hydrogenperoxide, and/or as additional water added along with the source oftransition metal ions and source of hydrogen peroxide. Typically, waterconstitutes at least about 50%, at least about 60%, at least about 70%,at least about 80%, at least about 90%, at least about 95%, at leastabout 98%, or at least about 99% by mass of the cleaning mixture.

After the pesticidal residue has been degraded, a waste mixturecomprising degradation products of the first pesticide is formed, whichshould be removed from the tank. Typically, the waste mixture is removedfrom the tank by spraying. Generally, a final water rinse following theaddition of the cleaning mixture is not required.

A significant advantage of the present invention, as compared to theprior art, is that the present methods may be performed in a relativelybrief amount of time. More particularly, it has been surprisinglydiscovered that Fenton-type chemistry is effective for degradation ofpesticidal residues over time scales such that tank cleaning methodsincorporating Fenton chemistry are dramatically shorter than the tankcleaning methods typically employed in the prior art. For example, theduration between introduction of the cleaning mixture into the tank andremoval of the waste mixture from the tank is typically less than about2 hours. Depending on the concentration of iron ions and hydrogenperoxide in the cleaning mixture, and the amount of pesticidal residuein the tank, the duration may be less than about 1 hour, less than about1 hour, less than about 30 minutes, less than about 25 minutes, lessthan about 20 minutes, less than about 15 minutes, less than about 10minutes, or even less than about 5 minutes.

In most cases, at least about 50% by weight, at least about 60% byweight, at least about 70% by weight, at least about 80% by weight, atleast about 90% by weight, at least about 95%, or at least about 99% byweight of the pesticidal residue is degraded prior to removal of thewaste mixture from the tank.

In various embodiments, a pre-rinse step is not incorporated and themethod proceeds over a duration of no more than about 30 minutes. Thatis, the waste mixture is removed from the tank (e.g., by spraying)within no more than about 30 minutes of introduction of the cleaningmixture into the tank (e.g., within no more than about 15 minutes or nomore than about 5 minutes). Further in accordance with such embodiments,suitable degradation of the pesticidal residue (e.g., at least about 70%or at least about 80% by weight) is achieved during such methods.

The method may generally be used to degrade various pesticides known inthe art. Typically, the first pesticide comprises one or more firstherbicides. Non-limiting examples of water-soluble herbicides that maybe degraded using the present methods include acifluorfen, acrolein,amitrole, asulam, benazolin, bentazon, bialaphos, bromacil, bromoxynil,chlorambenc, chloroacetic acid, clopyralid, 2,4-D, 2,4-DB, dalapon,dicamba, dichlorprop, difenzoquat, endothall, fenac, fenoxaprop,flamprop, flumiclorac, flumioxazin, fluoroglycofen, flupropanate,fomesafen, fosamine, fluroxypyr, glufosinate, glyphosate, imazameth,imazamethabenz, imazamox, imazapic, imazapyr, imazaquin, imazethapyr,ioxynil, MCPA, MCPB, mecoprop, methylarsonic acid, naptalam, nonanoicacid, picloram, quinclorac, sulfamic acid, 2,3,6-TBA, TCA, triclopyr andwater-soluble salts or esters thereof.

Non-limiting examples of water-insoluble herbicides that may be degradedusing the present methods include acetochlor, aclonifen, alachlor,ametryn, amidosulfuron, anilofos, atrazine, azafenidin, azimsulfuron,benfluralin, benfuresate, bensulfuron-methyl, bensulide, benzfendizone,benzofenap, bromobutide, bromofenoxim, butachlor, butafenacil,butamifos, butralin, butroxydim, butylate, cafenstrole,carfentrazone-ethyl, carbetamide, chlorbromuron, chloridazon,chlorimuron-ethyl, chlorotoluron, chlornitrofen, chlorotoluron,chlorpropham, chlorsulfuron, chlorthal-dimethyl, chlorthiamid,cinidon-ethyl, cinmethylin, cinosulfuron, clethodim,clodinafop-propargyl, clomazone, clomeprop, cloransulam-methyl,cyanazine, cycloate, cyclosulfamuron, cycloxydim, cyhalofop-butyl,daimuron, desmedipham, desmetryn, dichlobenil, diclofop-methyl,diflufenican, dimefuron, dimepiperate, dimethachlor, dimethametryn,dimethenamid, dinitramine, dinoterb, diphenamid, dithiopyr, diuron,EPTC, esprocarb, ethalfluralin, ethametsulfuron-methyl, ethofumesate,ethoxysulfuron, etobenzanid, fenoxaprop-ethyl, fenuron, flamprop-methyl,flazasulfuron, fluazifop-butyl, fluazifop-P-butyl, fluazoate,fluchloralin, flumetsulam, flumiclorac-pentyl, flumioxazin, fluometuron,fluorochloridone, flupoxam, flurenol, fluridone,fluroxypyr-I-methylheptyl, flurtamone, fluthiacet-methyl, graminicides,halosulfuron, haloxyfop, hexazinone, imazosulfuron, indanofan,isoproturon, isouron, isoxaben, isoxaflutole, isoxapyrifop, lenacil,linuron, mefenacet, metamitron, metazachlor, methabenzthiazuron,methyldymron, metobenzuron, metobromuron, metolachlor, S-metolachlor,metosulam, metoxuron, metribuzin, metsulfuron, molinate, monolinuron,naproanilide, napropamide, neburon, nicosulfuron, norflurazon,orbencarb, oryzalin, oxadiargyl, oxadiazon, oxasulfuron, pebulate,pendimethalin, pentanochlor, pentoxazone, phenmedipham, piperophos,pretilachlor, primisulfuron, prodiamine, profluazol, prometon,prometryn, propachlor, propanil, propaquizafop, propazine, propham,propisochlor, propyzamide, prosulfocarb, prosulfuron, pyraflufen-ethyl,pyrazogyl, pyrazolynate, pyrazosulfuron-ethyl, pyrazoxyfen, pyributicarb, pyridate, pyriminobac-methyl, quinclorac, quinmerac,quizalofop, quizalofop-P, rimsulfuron, sethoxydim, siduron, simazine,simetryn, sulcotrione, sulfentrazone, sulfometuron, sulfosulfuron,tebutam, tebuthiuron, tepraloxydim, terbacil, terbumeton,terbuthylazine, terbutryn, thenylchlor, thiazopyr, thidiazimin,thifensulfuron, thiobencarb, tiocarbazil, tralkoxydim, triallate,triasulfuron, tribenuron, trietazine, trifluralin, triflusulfuron andvernolate.

Preferably, the present method is effective to degrade the residue ofauxin herbicides. Exemplary auxin herbicides include2,4-dichlorophenoxyacetic acid (2,4-D), 4-(2,4-dichlorophenoxy)butanoicacid (2,4-DB), dichloroprop, (4-chloro-2-methylphenoxy)acetic acid(MCPA), 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB), mecoprop,dicamba, picloram, quinclorac, agriculturally acceptable salts or estersof any of these herbicides, and mixtures thereof.

The present method is particularly effective for the degradation ofdicamba and 2,4-D. Without being bound to any particular theory, it isbelieved that the dominant degradation pathway utilized by the presentmethod involves an attack on the ether linkages present in the dicambaand 2,4-D molecules. High-performance liquid chromatography (HPLC)analysis involving dicamba as described in the working examples hereinshows a decrease in the dicamba molecule concentration followed by acorresponding increase in the concentration of 2,4-dichlorosalicylate asa degradation product. In certain embodiments, in addition to dicamba or2,4-D, the present method is also effective for the degradation offlumioxazin.

The polyvalent iron ions may be derived from any water-soluble compoundcomprising iron in a +2 or +3 oxidation state. Suitable compoundsinclude ferric ammonium sulfate, ferric chloride, ferric oxide, ferricoxide hydrate, ferric sulfate, ferrous ammonium sulfate, ferrous oxide,ferrous chloride, ferrous sulfate and/or iron salts of di-, tri- orother polycarboxylic acids such as iron citrate. Ferrous sulfate, ferricchloride and iron citrate are preferred sources of iron ions for usewith the present method.

Ferrous sulfate is a particularly preferred source of iron ions. Ferroussulfate dissolves readily in water, and has been found to exhibitfavorable reaction kinetics as compared to other sources of polyvalentiron. Additionally, ferrous sulfate does not cause damage to mostplastics or stainless steel, materials which are commonly used inpesticidal tanks

The concentration of transition metal ions in the source of transitionmetal ions is typically at least about 5 grams per liter (g/L), at leastabout 7.5 g/L, at least about 10 g/L, at least about 12.5 g/L, at leastabout 15 g/L, at least about 17.5 g/L, at least about 20 g/L, or atleast about 25 g/L.

Aqueous hydrogen peroxide is readily available from commercialsuppliers, and is a preferred reagent for use with the present method.Alternatively, the method may utilize one or more compounds that reactor dissociate to produce hydrogen peroxide in an aqueous environment.Exemplary reagents of this type include sodium perborate, sodiumpercarbonate, and other sources of peroxides, such as adducts of ureaand peroxide.

Typically, hydrogen peroxide is incorporated into the cleaning mixturein a concentration of at least about 100 grams per liter of cleaningmixture. To reduce cleaning time and increase the rate of pesticidaldegradation, a higher concentration of hydrogen peroxide may beincorporated into the cleaning mixture. Typically, the concentration ofhydrogen peroxide in the source of hydrogen peroxide is at least about125 g/L, at least about 150 g/L, at least about 175 g/L, at least about200 g/L, at least about 225 g/L, or at least about 250 g/L.

In cases where it is possible to accurately estimate the amount ofpesticidal residue remaining in the tank, the amount of hydrogenperoxide added to the cleaning mixture may be adjusted accordingly.Typically, the molar ratio of hydrogen peroxide to residual pesticide isat least about 10:1, at least about 25:1, at least about 50:1, at leastabout 75:1, at least about 100:1, at least about 125:1, or at leastabout 150:1. Generally, higher hydrogen peroxide to pesticide ratiosprovide for faster degradation of the pesticidal residue.

In certain embodiments, the molar ratio of hydrogen peroxide to residualpesticide (e.g., first pesticide) is from about 10:1 to about 60:1, fromabout 10:1 to about 50:1, or from about 10:1 to about 40:1. In otherembodiments, the molar ratio of hydrogen peroxide to residual pesticide(e.g., first pesticide) is from about 15:1 to about 35:1, from about20:1 to about 35:1, or from about 25:1 to about 35:1. In still otherembodiments, the molar ratio of hydrogen peroxide to residual pesticide(e.g., first pesticide) is from about 10:1 to about 30:1, or from about10:1 to about 20:1.

Generally, the relative amounts of the hydrogen peroxide source and thetransition metal source are incorporated into the cleaning mixture suchthat the initial molar ratio of hydrogen peroxide to transition metalions is from about 500:1 to about 1:1. More typically, the initial molarratio of hydrogen peroxide to transition metal ions is at least about5:1, at least about 8:1, at least about 10:1, at least about 12:1, atleast about 15:1, at least about 20:1, at least about 25:1, or at leastabout 50:1 with hydrogen peroxide being in molar excess. As used herein,the term “initial molar ratio” at least refers to the molar ratio of thehydrogen peroxide to transition metal ions at the outset of the cleaningoperation (e.g., when the sources of hydrogen peroxide and transitionmetal ions are combined prior to initiation of the Fenton reaction).This does not, however, exclude the possibility that such molar ratiosmay persist during the cleaning operation. Typically, the source ofhydrogen peroxide will be added to the cleaning mixture in a mass ratioof at least about 0.5:1, at least about 1:1, at least about 2:1, atleast about 5:1, or at least about 10:1 as compared to the source oftransition metal ions.

Additional considerations may apply when the pesticidal residuecomprises a species that chelates or otherwise binds with free metalions in solution. For example, many phosphate-containing herbicides(e.g., glufosinate) are known to be effective chelators. A particularlynotable example of a species known to chelate free metal ions isN-(phosphonomethyl)glycine, commonly referred to as glyphosate.

Glyphosate is a highly effective and commercially important broadspectrum herbicide useful in controlling the growth of germinatingseeds, emerging seedlings, maturing and established woody and herbaceousvegetation, and aquatic plants. Glyphosate is used as a post-emergentherbicide to control the growth of a wide variety of annual andperennial grass and broadleaf weed species in cultivated crop lands,including cotton production, and is the active ingredient in the ROUNDUPfamily of herbicides available from Monsanto Company (Saint Louis, Mo.).

In addition to its herbicidal properties, glyphosate, by virtue of thepresence of carboxyl and a phosphonomethyl groups or ligands, canfunction as a strong complexing agent and can chelate or otherwise bindwith free metal ions in solution. In particular, glyphosate has beenobserved to chelate or bind with polyvalent iron ions, which arepreferred for use with the methods described herein. As a consequence,the present methods require more metal ions to be added to the cleaningmixture when glyphosate is present in the herbicidal residue tocompensate for this effect.

Frequently, herbicidal glyphosate formulations also contain relativelylow concentrations of N-(phosphonomethyl)iminodiacetic acid (PMIDA)and/or salts thereof which are intermediate compounds produced duringthe glyphosate manufacturing process. Like glyphosate, PMIDA alsochelates or binds with metal ions, and therefore also contributes to therequirement of additional transition metal ions added to the cleaningmixture.

For example, it has been observed that when no metal chelation ispresent (i.e., in the absence of glyphosate), suitable degradation ofdicamba residue may occur with very low amounts of metal catalyst in thecleaning mixture (e.g., <1 mM). In the presence of glyphosate, however,herbicidal degradation was only observed with cleaning mixtures havingtransition metal ion concentrations that provided at least a 1:1 molarratio of polyvalent iron ions to glyphosate, acid equivalent (a.e.).

Accordingly, when glyphosate is present, the molar ratio of transitionmetal ions to glyphosate is preferably greater than 1:1. Typically, theratio is at least about 2:1, at least about 3:1, or at least about 4:1.In certain embodiments, the molar ratio of transition metal ions toglyphosate is from about 1:1 to about 8:1, from about 1:1 to about 6:1,or from about 2:1 to about 4:1.

Generally, the methods of the present invention do not require the useof a pH adjusting agent. Aqueous solutions of iron (II), typicallyderived from a source such as ferrous sulfate, have been found to beeffective without adjustment of pH.

The use of a pH adjusting agent may be desirable, however, when aqueoussolutions of iron (III) are employed. At a pH of up to about 2, ferriciron has a strong tendency to hydrolyze to form a binuclear species,[Fe(H₂O)₄(OH)₂Fe(H₂O)₄]⁴⁺ and at a pH above about 2 to 3 polynuclearFe—OH species. The latter results in the precipitation of colloidal orhydrous ferric oxide.

The cleaning mixture preferably has a pH of from about 2 to about 4.Sodium hydroxide is typically used to raise the pH, if necessary, whilea lower pH is typically achieved through addition of the acidiccounterion corresponding to the iron source (e.g., H₂SO₄ when ferroussulfate is used, or HCl when ferric chloride is used). Glyphosate salts,if present in the herbicidal residue, typically act to buffer the systemto a pH of approximately 4.

As shown in Equation 1, reproduced below, the Fenton reaction involvesthe oxidation of ferrous iron ions by hydrogen peroxide to producehydroxyl radicals:

Fe²⁺+H₂O₂→Fe³⁺+OH⁻+OH.   (1)

This reaction requires stoichiometric amounts of Fe²⁺ and hydrogenperoxide to produce an equivalent molar quantity of hydroxyl radicals.The Fenton reaction is catalytic, however, to the extent that the iron(III) product compound is reduced in the presence of hydrogen peroxide:

Fe³⁺+H₂O₂→Fe²⁺+H⁺+HOO.   (2)

In the conventional Fenton process, reaction (2) is several orders ofmagnitude slower than reaction (1), and thus becomes the rate-limitingstep in environments where an excess of H₂O₂ is present. Alternativepathways for reduction of Fe(III) to Fe(II), however, are known in theart, and are predominantly used in many applications of Fenton chemistryfor water or soil treatment.

For example, an alternative version of reaction (2) uses photochemicalenergy, rather than ambient thermal energy, to reduce the Fe(III)species to Fe(II):

Fe³⁺+H₂O₂→^(bv)Fe²⁺+H⁺+HOO.   (2B)

In this reaction, the Fe(OH)²⁺ ion absorbs light at wavelengths up toabout 410 nm, which falls in the near-UV region of the spectrum. Thephotochemical reduction process including the combined process ofreactions (1) and (2B) is generally known as the photo-assisted Fenton(or photo-Fenton) reaction.

Advantageously, the present method has been shown to work without therequirement of UV lighting or other photons to assist the reaction. Thisis beneficial, in part, because the UV lighting and other equipmentrequired to carry out the photo-Fenton reaction can be fragile,unwieldy, and expensive, particularly when the reaction is scaled up tothe level required for the agricultural uses described herein.Experiments were conducted using foil-wrapped containers, wherein thepresent method was used to degrade herbicidal residue in the absence ofUV light. The foil-wrapped container results showed no significantdifferences in reaction kinetics as compared to equivalent experimentsconducted in the presence of UV light. As a result, the present methoddoes not require the cleaning mixture to be subjected to an artificiallight source while in the tank. The tank material may be substantiallyopaque to ultraviolet light. In addition, the present method is suitablefor use in large-scale agricultural operations.

As a further alternative to the UV-induced catalysis described above, anapplied electric current may be used to reduce the iron (III) species,thereby regenerating the iron ions in solution. Advantageously, thepresent method does not require the use of electrochemistry, in that itdoes not require the cleaning mixture to be subjected to an appliedelectric current while in the tank.

Kits

The present invention is further directed to kits for use in connectionwith the methods described herein.

Generally, the kit comprises a source of polyvalent iron ions and asource of hydrogen peroxide. The sources of polyvalent iron ions andhydrogen peroxide, respectively, may be selected as described above. Thekit may further comprise instructions for carrying out the methodsdescribed herein.

Typically, the source of hydrogen peroxide and the source of polyvalentiron ions should be packaged separately, such that they do not interactprior to the formation of the cleaning solution.

Following are Examples presented to illustrate the present invention andare not intended to limit the scope of this invention. The examples willpermit better understanding of the invention and perception of itsadvantages and certain variations of execution.

EXAMPLES Example 1

An experiment was conducted to measure the reaction kinetics of thepresent method with respect to dicamba. Ferric chloride (FeCl₃) was usedas the source of iron. Aqueous hydrogen peroxide (30% w/w) was used asthe peroxide source.

An additional sample was prepared with glyphosate to measure the effectof iron chelation on the dicamba degradation process.

Hydrogen peroxide was added to the reaction vessel in a molar ratio of100:1 with respect to dicamba. In the absence of glyphosate, the resultsshow that the dicamba concentration was degraded to below detectablelimits in 24 hours. In the sample containing glyphosate, however, thereaction was effectively stopped due to chelation of the iron species.The results of these trials are summarized in Table 1 below.

TABLE 1 100× Molar Ratio of Hydrogen Peroxide to Dicamba Over 24 HoursDicamba Dicamba Dicamba Dicamba Sam- % % % % ple Change Change ChangeChange No. Ingredients 0-2 Hr. 2-4 Hr. 4-6 Hr. 24 Hr. 723-10 glyphosate/ 4%  4%  5%  6% dicamba/ H₂O₂/FeCl₃ 723-11 dicamba/ 35% 58% 70% 92%H₂O₂/FeCl₃

Additional trials were conducted to evaluate the effectiveness of sodiumpercarbonate and OXICLEAN, respectively, as alternative sources ofhydrogen peroxide. The results of these trials are summarized in Table 2below.

TABLE 2 100× Molar Ratio of Hydrogen Peroxide to Dicamba Over 24 HoursDicamba Dicamba % Sample % Change No. Ingredients wt. 24 Hr. 24 Hr.723-16 glyphosate/dicamba/H₂O₂/FeCl₃ 0.116  7.9% 723-17dicamba/H₂O₂/FeCl₃ 0.01   92% 723-18 glyphosate/dicamba/ 0.103   18%2(Na₂CO₃)•3(H₂O₂)/FeCl₃ 723-19 dicamba/2(Na₂CO₃)•3(H₂O₂)/FeCl₃ 0.122  7% 723-20 glyphosate/dicamba/OXICLEAN/FeCl₃ ND  100% 723-21dicamba/OXICLEAN/FeCl₃ ND  100%

Example 2

Additional experiments were conducted to further investigate the effectof varying peroxide levels on the degradation reaction kinetics. Aqueoushydrogen peroxide, sodium percarbonate, and OXICLEAN were each used at100:1 and 10:1 molar ratios with respect to dicamba, in samples bothwith and without the presence of glyphosate. Control samples were alsoprepared with one or more herbicides in the absence of a source ofhydrogen peroxide, a source of iron, or both.

The samples were measured after 24 hours to determine the concentrationof dicamba remaining in the reaction mixture. The pH of the reactionmixture was also recorded. The results of these trials are summarized inTable 3, below.

TABLE 3 Degradation of Dicamba after 24 Hours Sample Iron Hydrogen %Change No. Herbicide(s) Source Peroxide Source dicamba pH 1435-1 DicambaNone None  0% 6.36 1435-6 Dicamba FeCl₃ H₂O₂ (100×)  8% 3.97 1435-24Dicamba FeCl₃ H₂O₂ (10×) 100% 1.84 1435-12 Dicamba FeCl₃ H₂O₂ (100×)100% 1.91 1435-18 Dicamba FeCl₃ H₂O₂ (100×) 100% 1.86 1435-20 DicambaFeCl₃ Sodium Percarb.  2% 10.78 (10×) 1435-14 Dicamba FeCl₃ SodiumPercarb.  9% 11.42 (100×) 1435-22 Dicamba FeCl₃ OXICLEAN (10×)  5% 10.931435-16 Dicamba FeCl₃ OXICLEAN 100% 10.82 (100×) 1435-7 Dicamba NoneSodium Percarb.  8% 11.54 (100×) 1435-8 Dicamba + None Sodium Percarb. 13% 10.51 Glyphosate (100×) 1435-23 Dicamba + FeCl₃ H₂O₂ (10×)  7% 3.38Glyphosate 1435-11 Dicamba + FeCl₃ H₂O₂ (100×)  12% 3.3 Glyphosate  1435-17 Dicamba + FeCl₃ H₂O₂ (100×)  11% 3.28 Glyphosate   1435-19Dicamba + FeCl₃ Sodium Percarb.  17% 9.43 Glyphosate (10×)   1435-13Dicamba + FeCl₃ Sodium Percarb.  25% 10.63 Glyphosate (100×)   1435-21Dicamba + FeCl₃ OXICLEAN (10×)  13% 10.32 Glyphosate 1435-15 Dicamba +FeCl₃ OXICLEAN 100% 10.84 Glyphosate (100×) 1435-2 Dicamba + None None 0% 4.29 Glyphosate   1435-10 Dicamba + FeCl₃ None  3% 3.51 Glyphosate  1435-3 Dicamba + None H₂O₂ (100×)  7% 4.14 Glyphosate 1435-9 Dicamba +None H₂O₂ + Sodium  17% 10.45 Glyphosate Percarb. (100×) 1435-5Dicamba + None OXICLEAN 100% 10.73 Glyphosate (100×) 1435-4 Dicamba +None Sodium Percarb.  9% 10.52 Glyphosate (100×) 1435-25 GlyphosateFeCl₃ Sodium Percarb. 11.12 (100×)

Example 3

An experiment was conducted to investigate whether the chelation effectof glyphosate can be overwhelmed by including additional amounts ofiron. Samples were prepared using ferric chloride (FeCl₃) and ferroussulfate (FeSO₄), respectively, which were incorporated at molar ratiosof 1:1 and 2:1 with respect to glyphosate.

Aqueous hydrogen peroxide (30% w/w) was used as the peroxide source, andwas provided in a 100:1 molar ratio with respect to dicamba. A smallnumber of control samples, as shown in the table below, were prepared inthe absence of a peroxide source.

For samples comprising both glyphosate and dicamba, the herbicides werepresent in a molar ratio of 1.5:1, respectively.

The results showed that at both 1:1 and 2:1 molar ratios of iron salt toglyphosate, the dicamba was fully degraded after 24 hours, with theconcentration being either not detectable (ND) or detectable but notquantifiable (<5 ppm) (DBNQ).

The results are summarized in Table 4, below. Iron concentration isprovided in terms of the molar ratio with respect to glyphosate. Whereno glyphosate is present, the concentrations used were either a 1.5:1molar ratio to dicamba (1×) or a 3:1 molar ratio to dicamba (2×).

TABLE 4 Effect of Iron Concentration on Dicamba Degradation Rate in thePresence of Glyphosate Dicamba Sample Peroxide Iron Iron % No.Herbicide(s) Conc. Source Conc. 24 Hr. 08578911-1 Dicamba None None —0.1021 08578911-2 Dicamba + Glyphosate None None — 0.1044 08578911-3Dicamba 100× None — 0.0952 08578911-4 Dicamba + Glyphosate 100× None —0.0981 08578911-5 Dicamba + Glyphosate None FeCl₃ 1X 0.0939 08578911-6Dicamba 100× FeCl₃ 1X DBNQ 08578911-7 Dicamba 100× FeCl₃ 2X 0.071108578911-8 Dicamba + Glyphosate 100× FeCl₃ 1X DBNQ 08578911-9 Dicamba +Glyphosate 100× FeCl₃ 2X ND 08578911-10 Dicamba + Glyphosate None FeSO₄1X 0.0924 08578911-11 Dicamba 100× FeSO₄ 1X ND 08578911-12 Dicamba 100×FeSO₄ 2X 0.0972 08578911-13 Dicamba + Glyphosate 100× FeSO₄ 1X DBNQ08578911-14 Dicamba + Glyphosate 100× FeSO₄ 2X ND

Example 4

Experiments were conducted using a dicamba/glyphosate tank mixformulation.

The herbicidal formulation was diluted to a concentration of 0.6% (g/g),which is appropriate for commercial spray applications. Furtherdilutions were made from this stock solution. Ferric chloridehexahydrate was provided by FISHER and diluted to a 10% (g/g) solutionon an anhydrous basis with distilled water. Aqueous hydrogen peroxide(30%) was provided by SIGMA-ALDRICH and was used as received.

Experiments were performed in the hood using 8 drachm (˜30 ml) glassvials. Reagents were added to the vials in the following order: dicambasolution, ferric chloride solution, and aqueous hydrogen peroxide. Onemilliliter samples were taken from each vial at 5, 15, 30, 60, and 120minute intervals and placed into HPLC vials containing a 10% solution ofN-(phosphonomethyl)iminodiacetic acid (PMIDA). The PMIDA quenched thereaction by rapidly chelating iron and preventing it from degradingperoxide. The amount of PMIDA solution in each vial was calculated suchthat the sum of the moles of glyphosate and PMIDA were a 10% excess ofthe moles of iron present.

Samples were analyzed using ion chromatography coupled with massspectroscopy (IC/MS/MS) to determine the dicamba concentration withtime. Results were reported on a mass basis in parts-per-million (ppm)of the sample.

Tables 5-7 summarize the experiments designed for analyzing the impactof initial iron, peroxide, and dicamba concentrations on dicambadegradation rates.

TABLE 5 Reagent amounts for experiments looking at the effect of initialiron concentration on dicamba degradation rate. Dicamba, Hydrogen 10%FeCl₃ PMIDA in analytical Sample ID mg/kg Peroxide, μL Solution, μLvial, uL 1.75XFe 1493.5 1725 960 125 2XFe 1493.5 1725 1097 125 2.5XFe1493.5 1725 1371 125 3XFe 1493.5 1725 1645 125

TABLE 6 Reagent amounts for experiments looking at the effect of initialperoxide concentration on dicamba degradation rate. (NBP 08615439)Dicamba, Hydrogen Iron, PMIDA in Sample ID mg/kg Peroxide, μL μLanalytical vial, uL 25XHOOH 1500 350 2200 160 50XHOOH 1500 700 2200 16075XHOOH 1500 1050 2200 160 100XHOOH 1500 1400 2200 160 125XHOOH 15001750 2200 160

TABLE 7 Reagent amounts for experiments looking at the effect of initialdicamba concentration on dicamba degradation rate. Sample Dicamba,Hydrogen Iron, PMIDA in ID mg/kg Peroxide, μL μL analytical vial, uL D/16000 3466 4458 400 D/2 3000 1733 2229 400 D/4 1500 867 1115 400 D/8 750433 557 400 D/16 375 217 279 400 D0 0 867 1115 400

Example 5

Using data generated in connection with the experiments described inExample 4, reaction kinetics were calculated for degradation of dicambain the presence of glyphosate. The results are generally consistent withfirst order kinetics for all of the reagents.

For example, FIG. 1 shows the expected concentration of dicamba withrespect to time on a logarithmic scale. The reaction rate constant(represented by the slope of the line) is not significantly impacted bythe initial dicamba concentration, implying first-order behavior. FIG. 2depicts the reaction rate constant as a function of initial hydrogenperoxide concentration. Generally, the data indicate that hydrogenperoxide has a first order effect on reaction rate. FIG. 3 depicts thereaction rate constant as a function of the iron to glyphosate molarratio. Note that approximately 1.56 molar equivalents of iron arerequired to start the reaction in the presence of glyphosate. Alsonoteworthy is that the impact of increasing iron concentration isapproximately 10 times greater than that achieved by increasing theconcentration of hydrogen peroxide.

The reaction rate can reasonably be described by the equation below

$\begin{matrix}{r_{d} = {{- \frac{\lbrack D\rbrack}{t}} = {{{k\left\lbrack {F - F_{0}} \right\rbrack}\lbrack P\rbrack}\lbrack D\rbrack}}} & (1)\end{matrix}$

Where D is the dicamba concentration in ppm, F is the molar ratio oftotal iron to glyphosate, and P is the peroxide concentration. From thekinetic data, k=7.2×10⁻⁷ min⁻¹ and F₀=1.56 mol iron/mol glyphosate. Therate equation is able to accurately fit the observations made inExamples 1-4 regarding changing peroxide and dicamba concentrations.

Example 6

The Fenton method, which was applied to degrade dicamba in Examples 1-4,was applied to 2,4-D to investigate whether this herbicide could also bedegraded. The solutions set forth in Table 8, below, were prepared andplaced in separate glass vials. The solutions were then analyzed by highperformance liquid chromatography at 12 days following the first mixing.As shown in the table below, no dicamba or 2,4-D was detected in any ofthe samples comprising Fenton reagents.

TABLE 8 Analysis of dicamba and 2,4-D samples 0.1% wt Dicamba acid 2,4-D10% w/w 30% w/w 0.1% wt 2,4-D (% wt/vol), (% wt/vol), Fe salt H₂O₂Clarity amine remaining remaining Sample # (μL) (μL) (g) (g) after 12days after 12 days 08488968-1 0 0 30 0 0.1058 ND (dicamba) 08488968-2 00 0 30 ND 0.1158 (2,4-D) 08488968-3 1050 1890 30 0 ND ND(dicamba/peroxide/ FeCl₃) 08488968-4 1050 1890 30 0 ND ND(dicamba/peroxide/ FeCl₃) 08488968-5 1050 1890 30 0 ND ND(dicamba/peroxide/ FeCl₃) 08488968-6 1050 1890 0 30 ND ND(2,4-D/peroxide/ FeCl₃) 08488968-7 1050 1890 0 30 ND ND (2,4-D/peroxide/FeCl₃) 08488968-8 1050 1890 0 30 ND ND (2,4-D/peroxide/ FeCl₃)

Example 7

The following tables represent exemplary formulations, applications, andenvironmental conditions of the compositions and methods describedherein. Unless otherwise noted, all values pertain to the cleaning of afull size spray tank with a capacity of 26 gallons (approximatelyequivalent to 100 kilograms).

TABLE 9 Dicamba Use Rate, lb/A 0.01 0.25 0.5 Glyphosate Use Rate, lb/A0.03 0.75 1.5 FeCl₃, molar equivalent to glyphosate 1 1.25 1.5 HydrogenPeroxide, molar eq. to dicamba 25 50 100 Temperature, C. 15 25 35

TABLE 10 Dicamba Use Rate, lb/acre 0.25 0.5 0.05 0.005 0.4518 2.56E−04Application Rate, gallons/acre 10 10 10 10 10 10 Dicamba Concentration,% (g/g) 0.2998 0.5995 0.0600 0.0060 0.5417 3.069 × 10⁻⁶ Holdup Volume,gallons 6 6 6 6 6 6 Rinse Volume, gallons 20 20 20 20 20 20 Rinse 1Dicamba Concentration, 691.75 1383.5 138.35 13.835 1250 0.70836 mg/kg

TABLE 11 Glyphosate Use Rate, lb/acre 0.75 1.5 0.15 0.015 1.355 1Application Rate, gallons/acre 10 10 10 10 10 10 GlyphosateConcentration, % (g/g) 0.899 1.799 0.180 0.018 1.625 1.199 HoldupVolume, gallons 6 6 6 6 6 6 Rinse Volume, gallons 20 20 20 20 20 20Rinse 1 Dicamba Concentration, 2075.3 4150.5 415.05 41.505 3750 2767.02mg/kg

Tables 12A and 12B generally relate to an application of the presentmethod to clean a full size spray tank, wherein the source of transitionmetal ions is ferric chloride, and the source of hydrogen peroxide isaqueous hydrogen peroxide. In addition to glyphosate acid, a relativelysmall amount N-(phosphonomethyl)iminodiacetic acid, an intermediateproduced during the production of glyphosate that is present in someglyphosate formulations, was also incorporated into the test herbicidalmixture. The test mixture was also pH adjusted to approximately 4.0using sodium hydroxide, as necessary.

TABLE 12A Dicamba, mg/kg 1500 Glyphosate, mg/kg 3035.16 FeCl₃ BasisAmount, mol/mol glyphosate 1.3 H₂O₂ Basis Amount, mol/mol dicamba 25

TABLE 12B Amount Density Mass Amount MW Amount Conc. Conc. Component(uL) (mg/ul) Frac. (mg) (g/mol) (mmol) (mol/L) (mg/kg) Dicamba acid30000 1 0.0015 45 221.04 0.20 0.01 1456 Glyphosate 30000 1 0.003 91.05169.07 0.54 0.02 2946 acid FeCl₃ 392 2.898 0.1 113.56 162.2 0.70 0.023674 (10% soln) H₂O₂ 520 1.11 0.3 173.12 34.015 5.09 0.16 5600 (30%soln) Total 30912 422.73 PMIDA 10% 429 1 0.094 40.36 227.11 0.185.67E−03 1288 (g/g) solution

Tables 13A and 13B generally relate to an application of the presentmethod to clean a full size spray tank, wherein the source of transitionmetal ions is ferrous sulfate, and the source of hydrogen peroxide isaqueous hydrogen peroxide.

TABLE 13A Dicamba Basis, mg/kg 1250 Glyphosate Basis, mg/kg 3750 FeCl₃Basis Amount, uL 50 H₂O₂ Basis Amount, uL 567

TABLE 13B Amount Density Mass Amount MW Amount Conc. Conc. Component(uL) (mg/ul) Frac. (mg) (g/mol) (mmol) (mol/L) (mg/kg) Dicamba acid30000 1 0.0013 37.5 221.04 0.17 4.77 × 10⁻³ 1055 Glyphosate 30000 10.0038 112.5 169.07 0.67 0.02 3164 acid FeSO₄•7H₂O 3662 1.898 0.1 695.03278.02 2.50 0.07 19550 (10% soln) Hydrogen 1890 1.11 0.3 629.37 34.01518.50 0.52 17703 Peroxide (30% soln) Total 35552 1474.41

Tables 14A and 14B generally relate to an application of the presentmethod to clean a full size spray tank, wherein the source of transitionmetal ions is ferric chloride, and the source of hydrogen peroxide issodium perborate.

TABLE 14A Dicamba Basis, mg/kg 1250 Glyphosate Basis, mg/kg 3750 FeCl₃Basis Amount, uL 50 H₂O₂ Basis Amount, uL 567

TABLE 14B Amount Density Mass Amount MW Amount Conc. Conc. Component(uL) (mg/ul) Frac. (mg) (g/mol) (mmol) (mol/L) (mg/kg) Dicamba acid30000 1 0.0013 37.5 221.04 0.17 0.01 1143 Glyphosate 30000 1 0.0038112.5 169.07 0.67 0.02 3430 acid FeCl₃ 1400 2.898 0.1 405.72 162.2 2.500.08 12369 (10% soln) Sodium 1401 1.31 1 1835.57 100 18.36 0.56 55961Perborate (μg) Total 32801 2391.29

Tables 15A and 15B generally relate to an application of the presentmethod to clean a full size spray tank, wherein the source of transitionmetal ions is ferric chloride, and the source of hydrogen peroxide isaqueous hydrogen peroxide. In addition to glyphosate acid, a relativelysmall amount N-(phosphonomethyl)iminodiacetic acid, an intermediateproduced during the production of glyphosate that is present in someglyphosate formulations, was also incorporated into the test herbicidalmixture. The test mixture was also pH adjusted to approximately 4.0using sodium hydroxide.

TABLE 15A Dicamba, mg/kg 1500 Glyphosate, mg/kg 3035.15625 FeCl₃ BasisAmount, mol/mol glyphosate 4 H₂O₂ Basis Amount, mol/mol dicamba 125

TABLE 15B Amount Density Mass Amount MW Amount Conc. Conc. Component(uL) (mg/ul) Frac. (mg) (g/mol) (mmol) (mol/L) (mg/kg) Dicamba acid50000 1 0.0015 75 221.04 0.34 5.66 × 10⁻³ 1252 Glyphosate 50000 10.00303 151.757 169.07 0.90 1.50 × 10⁻² 2533 acid FeCl₃ 5573 1.045 0.1582.37 162.2 3.59 5.99 × 10⁻² 9721 (10% soln.) Hydrogen 4332 1.11 0.31,442.67 34.015 42.41 0.708 24083 Peroxide (30% soln) Total 599052251.79 PMIDA 10% 9542 1 0.094 896.96 227.11 3.95 5.69 × 10⁻² 12916(g/g) soln.

Tables 16A and 16B generally relate to an application of the presentmethod to clean a full size spray tank, wherein the source of transitionmetal ions is ferric chloride, and the source of hydrogen peroxide isaqueous hydrogen peroxide. In addition to glyphosate acid, a relativelysmall amount N-(phosphonomethyl)iminodiacetic acid, an intermediateproduced during the production of glyphosate that is present in someglyphosate formulations, was also incorporated into the test herbicidalmixture. The test mixture was also pH adjusted to approximately 4.0using sodium hydroxide.

TABLE 16A Dicamba, mg/kg 1500 Glyphosate, mg/kg 3035.15625 FeCl₃ BasisAmount, mol/mol glyphosate 4 H₂O₂ Basis Amount, mol/mol dicamba 125

TABLE 16B Amount Density Mass Amount MW Amount Conc. Conc. Component(uL) (mg/ul) Frac. (mg) (g/mol) (mmol) (mol/L) (mg/kg) Dicamba acid50000 1 0.0015 75 221.04 0.34 5.66 × 10⁻³ 1252 Glyphosate 50000 1 3.03 ×10⁻³ 151.757 169.07 0.90 1.50 × 10⁻² 2533 acid FeCl₃ 5573 1.045 0.1582.37 162.2 3.59 5.99 × 10⁻² 9721 (10% soln.) Hydrogen 4332 1.11 0.31442.67 34.015 42.41 0.708 24083 Peroxide (30% soln) Total 59905 2251.79PMIDA 10% 9542 1 0.094 896.96 227.11 3.95 5.69 × 10⁻² 12916 (g/g) soln.

Example 8

This example describes a small-scale demonstration of the efficacy ofthe present invention in largely eliminating injury to soy due toresidual levels of three herbicides: dicamba, 2,4-D and flumioxazin, allin the presence of glyphosate. Four simulated spray solutions wereprepared. All of the solutions were prepared assuming a 10 gallon/acrespray rate with a glyphosate rate of 1.0 lb acid equivalent (a.e.) peracre (1120 g/ha). The source of the glyphosate was Roundup Powermax®herbicide. In addition, the spray solutions contained dicambadiglycolamine salt (Clarity®) or 2,4-D amine sometimes in combinationwith flumioxazin derived from Valor® herbicide.

60 ml of the simulated spray solutions were transferred to 250 mlbeakers. A ferrous sulfate solution (10% iron) was added to eachsolution in an amount that provided 3 moles of iron per mole ofglyphosate. 30 moles of hydrogen peroxide per mole of dicamba or 15 or30 moles of hydrogen peroxide per mole of 2,4-D was then added. Theflask was swirled and allowed to stand for 20 minutes. Oxygen evolutionoccurred with mild foaming.

Immediately after 20 minutes had elapsed, the treated solutions werediluted 30x and sprayed over glyphosate-tolerant soybeans at a 10 gallonper acre rate. As a control, untreated solution, was diluted 30x andsprayed at the same rate. Soybean injury was rated 7 days afterspraying. Injury to soy was dramatically reduced in all cases.

TABLE 17 Treatment protocols and soy injury ratings for simulated tankcleaning Treat- Injury ment Glyphosate Other Rates H₂O₂ un- Injury No.rate (g/ha) herbicides (g/ha) ratio^(†) treated treated 1 1120 Dicamba 560 30 26% 4% 3 1120 Dicamba/  560/107 30 28% 7% flumi* 4 1120 2,4-D1120 30 38% 4% 5 1120 2,4-D 1120 15 38% 3% 6 1120 2,4-D/ 1120/107 30 24%4% flumi* *flumi = flumioxazin. ^(†)Molar ratio of H₂O₂ to dicamba or2,4-D.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above products and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

1. A method of preparing a tank for use in connection with a secondpesticide following use of the tank in connection with a firstpesticide, the method comprising: introducing a cleaning mixture into atank containing a residual amount of the first pesticide, wherein thecleaning mixture comprises (a) a source of transition metal ions, and(b) a source of hydrogen peroxide; allowing the cleaning mixture toremain in the tank for a time sufficient to degrade at least a portionof the residual amount of the first pesticide, thereby forming a wastemixture comprising degradation products of the first pesticide; andremoving the waste mixture from the tank.
 2. The method of claim 1wherein the cleaning mixture further comprises water.
 3. The method ofclaim 1 wherein the first pesticide comprises a first herbicide. 4-5.(canceled)
 6. The method of claim 3 wherein the first herbicidecomprises an herbicide selected from the group consisting of 2,4-D,dicamba, and mixtures thereof.
 7. The method of claim 3 wherein thefirst herbicide comprises dicamba. 8-14. (canceled)
 15. The method ofclaim 1 wherein the source of transition metal ions comprises a sourceof polyvalent iron ions.
 16. (canceled)
 17. The method of claim 15wherein the source of iron ions is ferrous sulfate, ferric chloride, ora mixture thereof. 18-19. (canceled)
 20. The method of claim 1 whereinthe source of hydrogen peroxide is selected from the group consisting ofsodium percarbonate, sodium perborate, and combinations thereof.
 21. Themethod of claim 1 wherein the source of hydrogen peroxide is aqueoushydrogen peroxide.
 22. The method of claim 1 wherein the durationbetween introduction of the cleaning mixture into the tank and removalof the waste mixture from the tank is less than about 2 hours.
 23. Themethod of claim 1 wherein the waste mixture is removed from the tank byspraying.
 24. (canceled)
 25. The method of claim 1 further comprising apre-rinse step prior to introducing the cleaning mixture into the tank,wherein the pre-rinse comprises introducing an aqueous medium into thetank to form a diluted pesticidal residue mixture comprising a portionof the first pesticide. 26-27. (canceled)
 28. The method of claim 25wherein at least a portion of the diluted pesticidal residue mixture isremoved from the tank by spraying prior to introduction of the cleaningmixture into the tank.
 29. The method of claim 2 wherein waterconstitutes at least about 50%, at least about 60%, at least about 70%,at least about 80%, at least about 90%, at least about 95%, at leastabout 98%, or at least about 99% by weight of the cleaning mixture. 30.The method of claim 1 wherein the cleaning mixture is not subjected toan artificial light source or an applied electric current while in thetank. 31-37. (canceled)
 38. The method of claim 1 wherein the initialmolar ratio of hydrogen peroxide to transition metal ions in thecleaning mixture is at least about 5:1.
 39. (canceled)
 40. The method ofclaim 1 wherein the molar ratio of hydrogen peroxide introduced into thetank to residual first pesticide is at least about 10:1. 41-44.(canceled)
 45. The method of claim 1 wherein the first pesticidecomprises glyphosate.
 46. (canceled)
 47. The method of claim 45 whereinthe cleaning mixture comprises transition metal ions in a molar ratio ofat least about 2:1 with respect to the amount of glyphosate present inthe pesticidal residue prior to introduction of the cleaning mixtureinto the tank.
 48. (canceled)
 49. A kit for use in cleaning a tankfollowing the use of the tank in connection with a herbicidalcomposition comprising dicamba, wherein the kit comprises a source ofhydrogen peroxide and a source of transition metal ions. 50-64.(canceled)